Systems For Etching A Substrate Using A Hybrid Wet Atomic Layer Etching Process

ABSTRACT

The present disclosure provides a system for etching an exposed material on a substrate disposed within a process chamber using a hybrid atomic layer etching (ALE) process that combines a gas-phase surface modification step with a liquid-phase dissolution step within the same process chamber. In the hybrid ALE process disclosed herein, a gas-phase reactant is used to modify an exposed surface of the material to create a modified surface layer, and one or more liquid-phase reactants are used to selectively dissolve the modified surface layer without dissolving the material underlying the modified surface layer. Once the modified surface layer is selectively dissolved, the substrate may be dried and the gas-phase surface modification and liquid-phase dissolution steps may be repeated for one or more ALE cycles until a desired amount of the material is etched.

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 63/151,579, filed Feb. 19, 2021, entitled “Hybrid Wet AtomicLayer Etching”; the disclosure of which is expressly incorporatedherein, in their entirety, by reference. This application further claimspriority to, and is a continuation-in-part of, U.S. patent applicationSer. No. 16/402,611, filed May 3, 2019, entitled “Processing System andPlatform for Wet Atomic Layer Etching Using Self-Limiting andSolubility-Limited Reactions,” which is a continuation-in-partapplication of U.S. patent application Ser. No. 16/287,658, filed Feb.2, 2019, entitled “Wet Atomic Layer Etching Using Self-Limiting andSolubility-Limited Reactions,” now U.S. Pat. No. 10,982,335, whichclaims priority to U.S. Provisional Patent Application No. 62/767,808,entitled, “Wet Atomic Layer Etching Using Self-Limiting andSolubility-Limited Reactions” filed Nov. 15, 2018; the disclosure ofwhich are expressly incorporated herein, in their entirety, byreference.

BACKGROUND

The present disclosure relates to the processing of substrates. Inparticular, it provides a method of etching of layers on substrates.

As geometries of substrate structures continue to shrink and the typesof structures evolve, the challenges of etching substrates haveincreased. One technique that has been utilized to address thesechallenges is atomic layer etching (ALE). ALE processes are generallyknown to involve processes which remove thin layers sequentially throughone or more self-limiting reactions. For example, ALE typically refersto techniques that can etch with atomic precision, i.e., by removingmaterial one or a few monolayers at a time. ALE processes generally relyon a chemical modification of the surface to be etched followed by aselective removal of the modified layer. Thus, ALE processes offerimproved performance by decoupling the etch process into sequentialsteps of surface modification and removal of the modified surface. Suchprocesses often include multiple cyclic series of layer modification andetch steps, where the modification step modifies the exposed surfacesand the etch step selectively removes the modified layer. Thus, in someALE processes, a series of self-limiting reactions may occur and thecycle may be repeatedly performed.

A variety of ALE processes are known, including plasma ALE, thermal ALEand wet ALE techniques. In plasma ALE, a target substrate disposedwithin a process chamber is exposed to a reactive precursor, whichadsorbs on and reacts with the exposed surfaces of the target substrateto modify the surface in a surface modification step. The exposedsurfaces of the target substrate are then bombarded with low energynon-reactive ions (e.g., from an inert gas) to remove the modifiedsurface layer in a subsequent etch step. Some plasma ALE processes use acyclic pulsing of process gases (e.g., reactive precursor gas(es) and aninert gas(es)) within one or more ALE cycles—where each ALE cycleconsists of at least one surface modification step and etch step—toremove material from the surface of the target substrate. In plasma ALE,operating variables (e.g., the chamber temperature, chamber pressure,flowrates of process gases, types of process gases, and/or otheroperating variables) can be adjusted to control the surface modificationand etch process steps. In some cases, a plasma ALE process may beperformed at relatively high temperature and/or pressure. In plasma ALE,the process chamber is often purged after each surface modification stepand after each etch step to avoid mixing reactive precursors and inertgases within the process chamber. This increases the cycle time andreduces throughput.

In thermal ALE, the modified layer is removed through volatilizationwhen material is taken from the solid phase into the gas phase. Thisphase change requires the addition of latent heat and is limited by thevapor pressure of the modified layer. Thermal energy is used to replacethe intermolecular interactions that stabilize the modified layer on thesurface. In thermal ALE, high temperatures are often required to removethe modified layer.

In wet ALE, material is removed from a surface in a cyclic processutilizing self-limiting and selective reactions. The name “wet ALE”indicates that some, if not all, of the reactions take place in theliquid phase. One advantage of wet ALE over thermal or plasma ALEtechniques is that wet ALE processes can be run at atmospherictemperature and pressure.

The wet ALE process begins with a self-limiting surface modificationstep, which can be achieved through oxidation, reduction, ligandbinding, or ligand exchange. Ideally, the modified layer is confined tothe top monolayer of the material and acts as a passivation layer toprevent the modification reaction from progressing further. The secondstep of the wet ALE process is selective dissolution of the modifiedlayer. The process must dissolve the modified layer without removing anyof the underlying unmodified material. This can be accomplished by usinga different solvent in the second step than was used in the first step,changing the pH, or changing the concentration of other components inthe first solvent.

In wet ALE, purge steps are performed in between the surfacemodification step and the selective dissolution step, typically byrinsing the modified surface layer with a purge solution to removeexcess reactants. The purpose of the purge step is to ensure that thereis no mixing between the solution used for surface modification and thesolution used for dissolution. If these two solutions mix, it ispossible that solution mixture can both modify and dissolve thesubstrate. Mixing the solutions prevents the modification reaction frombeing self-limiting and lead to continuous etching. Continuous etchestend to preferentially etch at grain boundaries, which results in arough post-etch surface.

Being an atomic layer process, wet ALE tends to be slow. Each reactionmust have enough time to be driven to saturation and each purge stepmust be sufficient to completely separate the surface modificationsolution and the dissolution solution. This can lead to low throughputin high volume manufacturing (HVM) making wet ALE an expensive process.

SUMMARY

One advantage of wet ALE over thermal or plasma ALE techniques is that awet ALE process can be run at atmospheric temperature and pressure.Gas-phase reactants, condensates, sprays or mists can be used in a wetALE process while maintaining these advantages as long as the reactantsare delivered near room temperature and near atmospheric pressure. ForALE of metals, oxidation is often used as a surface modification step,and many self-limiting oxidation processes occur on metal surfaces usingroom temperature, atmospheric pressure reactants.

As described further herein, the present disclosure maintains theadvantages of wet ALE (e.g., self-limiting reactions at near atmosphericpressure and temperature, smoothing of the post-etch surface, digitalcontrol over the total etch amount, etc.), while avoiding thedisadvantages thereof (e.g., low throughput, high cost, etc.), byproviding a hybrid wet ALE process that combines a gas-phase surfacemodification step with a liquid-phase dissolution step for etching asubstrate disposed within a process chamber. In the hybrid ALE processdescribed herein, a gas-phase reactant is used to modify an exposedsurface of a material to create a modified surface layer, and one ormore liquid-phase reactants are used to selectively dissolve themodified surface layer without dissolving the material underlying themodified surface layer. Once the modified surface layer is selectivelydissolved, the substrate may be dried and the gas-phase surfacemodification and liquid-phase dissolution steps may be repeated for oneor more ALE cycles until a desired amount of the material is etched.

In some embodiments, the exposed surface of the material may be exposedto the gas-phase reactant and the liquid-phase reactant(s) in sequence.In other embodiments, the exposed surface of the material may be exposedto the liquid-phase reactant(s), while a gas-phase reactant is suppliedto the process chamber. When a liquid-phase reactant is dispensed in thepresence of a gas-phase reactant, the liquid-phase reactant dispensedonto the exposed surface of the material displaces the gas-phasereactant from the exposed surface to prevent further surfacemodification of the exposed surface. When dispensed in such a manner,the liquid-phase reactant not only dissolves the modified surface layer,but also partitions the gas-phase surface modification and liquid-phasedissolution steps. This decreases the cycle time and improves thethroughput of the hybrid ALE process described herein, compared to otherALE techniques, by avoiding the need to perform a purge step between thesurface modification and dissolution steps.

Cycle time and throughput may be further improved in the hybrid ALEprocess described herein by performing the gas-phase surfacemodification and liquid-phase dissolution steps within the same processchamber. In one example implementation, the gas-phase surfacemodification and liquid-phase dissolution steps may both be performedwithin a spin chamber. In some embodiments, the gas-phase surfacemodification and liquid-phase dissolution steps may be performed withinthe same process chamber at roughly the same temperature and pressure.In one example implementation, the gas-phase surface modification andliquid-phase dissolution steps may be performed at (or near) atmosphericpressure and room temperature. Performing the gas-phase surfacemodification and liquid-phase dissolution steps within the same processchamber at roughly the same temperature and pressure decreases the cycletime and improves the throughput of the hybrid ALE process describedherein by avoiding unnecessary chamber transitions andtemperature/pressure changes.

The hybrid ALE process described herein may be used for etching a widevariety of materials including polycrystalline materials,single-crystalline materials and amorphous materials. In someembodiments, the hybrid ALE process described herein may be used foretching a polycrystalline material, such as a transition metal (such as,e.g., molybdenum, Mo), and a gas-phase oxidizing agent (e.g., oxygen,O₂, or ozone, O₃) may be used to oxidize an exposed surface of thetransition metal to form a self-limiting oxidized layer (such as, e.g.,MoO₃). The oxidation of transition metals, such as molybdenum, isself-limiting at (or near) room temperature. After the exposed surfaceof the transition metal is exposed to the gas-phase oxidizing agent andthe oxidized layer is formed, a liquid-phase reactant may be dispensedonto the substrate to selectively dissolve the oxidized layer, so thatthe oxidized layer is removed without etching the underlyingpolycrystalline material. Several chemistries can be used to selectivelydissolve molybdenum oxides (e.g., MoO₃) without dissolving metallic Moare described in more detail below.

Example process conditions (e.g., etch chemistry, temperature, pressure,etc.) are provided herein for etching transition metals, and morespecifically, for etching molybdenum using the hybrid ALE processdescribed herein. It will be recognized by those skilled in the art,however, that the disclosed process is not strictly limited to theexample process conditions described herein and may be performed using awide variety of process conditions depending on the material beingetched. In general, the hybrid ALE process described herein may use aminimum pressure, which is greater than the vapor pressure of theliquid-phase reactant used to remove and/or dissolve the modifiedsurface layer. However, the temperature used in the hybrid ALE processdescribed herein may generally range between the melting point and theboiling point of the liquid-phase reactant.

Thus, in some embodiments of the present disclosure, atmosphericpressure, room temperature, gas-phase reactants (or, condensates, spraysor mists) may be added to the wet ALE process to create a hybrid ALEprocess, which improves upon other ALE techniques by decreasing cycletime and increasing throughput while maintaining the advantages ofconventional wet ALE.

Various embodiments of a system are provided herein to etch a substrateusing a hybrid atomic layer etching (ALE) process. In each embodiment,the system may generally include: a process chamber configured toreceive the substrate; a gas supply system coupled to the processchamber and configured to store a gas-phase reactant; a chemical supplysystem coupled to the process chamber and configured to store one ormore liquid-phase reactants; and a controller programmed to controlprocess conditions within the process chamber while multiple cycles ofthe hybrid ALE process are performed to etch a material exposed on thesubstrate, wherein each cycle includes a gas-phase surface modificationstep and a liquid-phase dissolution step.

According to a first embodiment of the system described herein, thecontroller may be configured to supply a first set of control signals tothe gas supply system during the gas-phase surface modification step,and a second set of control signals to the chemical supply system duringthe liquid-phase dissolution step. The first set of control signals maycause the gas supply system to introduce the gas-phase reactant into theprocess chamber to expose the substrate to the gas-phase reactant,chemically modify an exposed surface of the material and provide amodified surface layer of the material. The second set of controlsignals may cause the chemical supply system to dispense the one or moreliquid-phase reactants onto a surface of the substrate to selectivelydissolve the modified surface layer without dissolving the materialunderlying the modified surface layer.

In some embodiments, the gas-phase reactant introduced into the processchamber during the gas-phase surface modification step may be agas-phase oxidizing agent, which oxidizes the exposed surface of thematerial to form a self-limiting oxide layer. In some embodiments, theprocess chamber further may further include a gas inlet, which iscoupled to receive the gas-phase oxidizing agent from the gas supplysystem. In such embodiments, the gas inlet may be configured tointroduce the gas-phase oxidizing agent into the process chamber tocreate an oxygen-containing gaseous environment within the processchamber. In other embodiments, the process chamber may further include agas nozzle, which is coupled to receive the gas-phase oxidizing agentfrom the gas supply system. In such embodiments, the gas nozzle may beconfigured to translate over the surface of the substrate to dispensethe gas-phase oxidizing agent onto the surface of the substrate.

In some embodiments, the one or more liquid-phase reactants may includean aqueous solution, which selectively dissolves and removes theself-limiting oxide layer without dissolving the material underlying theself-limiting oxide layer.

In some embodiments, the one or more liquid-phase reactants may includea complexing agent dissolved in a first liquid solvent, wherein thecomplexing agent binds to the self-limiting oxide layer to form aligand-metal complex. In some embodiments, the ligand-metal complex maybe soluble in the first liquid solvent. In such embodiments, the firstliquid solvent may dissolve the ligand-metal complex and remove theself-limiting oxide layer.

In some embodiments, the one or more liquid-phase reactants may furtherinclude a second liquid solvent, which is different from the firstliquid solvent. The ligand-metal complex may be insoluble in the firstliquid solvent and soluble in the second liquid solvent. In suchembodiments, wherein the second liquid solvent may dissolve theligand-metal complex and remove the self-limiting oxide layer.

In some embodiments, each cycle of the hybrid ALE process may furtherinclude a drying step, which is used to dry the surface of the substrateafter the liquid-phase dissolution step is performed to dissolve themodified surface layer. In some embodiments, for example, the processchamber may include a gas inlet or a gas nozzle, which is configured tosupply a gas stream of air or nitrogen to the substrate to dry thesurface of the substrate. In other embodiments, the process chamber mayinclude a spinner configured to rotate at a rotational speed, whereinthe substrate is held on the spinner, and wherein the controller isconfigured to control the rotational speed of the spinner to dry thesurface of the substrate.

According to a second embodiment of the system described herein, thecontroller may be configured to supply a first set of control signals tothe gas supply system during the gas-phase surface modification step,and a second set of control signals to the chemical supply system duringthe liquid-phase dissolution step, as described above. In addition, thecontroller may be programmed to control timing of the gas-phase surfacemodification step and the liquid-phase dissolution step performed duringeach cycle of the hybrid ALE process, so that the one or moreliquid-phase reactants are dispensed onto the surface of the substratewhile the substrate is exposed to the gas-phase reactant. The one ormore liquid-phase reactants dispensed during the liquid-phasedissolution step may segregate the gas-phase surface modification stepfrom the liquid-phase dissolution step by displacing the gas-phasereactant from the surface of the substrate.

In some embodiments, the process chamber may include a spinnerconfigured to rotate at a rotational speed, wherein the substrate isheld on the spinner. In such embodiments, the controller may control therotational speed of the spinner during the liquid-phase dissolutionstep, so that the one or more liquid-phase reactants are dispensed ontothe surface of the substrate in the presence of the gas-phase reactantwhile the spinner is rotating at a first rotational speed. Rotation ofthe spinner at the first rotational speed may cause the one or moreliquid-phase reactants to propagate outward along the surface of thesubstrate to dissolve the modified surface layer and prevent thegas-phase reactant from reaching the surface of the substrate andre-oxidizing underlying portions of the substrate.

After the liquid-phase dissolution step is performed to selectivelydissolve the modified surface layer, the controller may control therotational speed of the spinner during a spin drying step to flush theone or more liquid-phase reactants from the surface of the substrate andre-expose the exposed surface of the material to the gas-phase reactantin a subsequent gas-phase surface modification step. In someembodiments, the controller may control the rotational speed of thespinner during the spin drying step, so that the spinner rotates at asecond rotational speed, which is greater than the first rotationalspeed.

According to a third embodiment of the system described herein, thecontroller may be configured to supply a first set of control signals tothe gas supply system during the gas-phase surface modification step,and a second set of control signals to the chemical supply system duringthe liquid-phase dissolution step, as described above. In addition, thecontroller may be programmed to control a temperature and a pressurewithin the process chamber, so that the gas-phase surface modificationstep and the liquid-phase dissolution step are performed at roughly thesame temperature and the same pressure.

In some embodiments, the controller may be programmed to control thetemperature and the pressure within the process chamber, so that thegas-phase surface modification step and the liquid-phase dissolutionstep are both performed at or near atmospheric pressure and roomtemperature. In other embodiments, the controller may be programmed tocontrol the temperature and/or the pressure within the process chamber,so that the temperature and/or the pressure changes no more than 20%between the gas-phase surface modification step and the liquid-phasedissolution step.

The system disclosed herein may be used to etch a wide variety ofmaterials, including polycrystalline materials, single-crystallinematerials and amorphous materials. In some embodiments, the systemdisclosed herein may be used to etch a polycrystalline metal materialsuch as, for example, a transition metal. Examples of transition metalsthat may be etched using the system disclosed herein include, but arenot limited to, molybdenum (Mo), tungsten (W), vanadium (V), niobium(Nb), tantalum (Ta), and chromium (Cr).

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present inventions and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features. It is to be noted, however, that theaccompanying drawings illustrate only exemplary embodiments of thedisclosed concepts and are therefore not to be considered limiting ofthe scope, for the disclosed concepts may admit to other equallyeffective embodiments.

FIG. 1 illustrates one example of a cyclic hybrid atomic layer etching(ALE) process in accordance with the present disclosure.

FIG. 2A is a graph depicting exemplary etch amounts (expressed innanometers, nm) that may be achieved over time (expressed in minutes,min) when attempting to etch a molybdenum (Mo) surface using: (a)UV-ozone oxidation alone, and (b) a solution of α-benzoin oxime andDMSO.

FIG. 2B is a graph depicting exemplary etch amounts (nm) that may beachieved as a function of cycle number for when a UV-ozone oxidationstep, an α-benzoin oxime ligand binding (complexation) step and DMSOdissolution step are used to etch a Mo surface using the hybrid ALEprocess disclosed herein

FIG. 3A is a block diagram illustrating one embodiment of a processingsystem that may use the hybrid ALE process disclosed herein to etch amaterial on a surface of a substrate.

FIG. 3B is a magnified view of a portion of the substrate shown in FIG.3A illustrating how the gas-phase surface modification and liquid-phasedissolution steps are partitioned within the hybrid ALE processdisclosed herein.

FIG. 3C is a top down view into the processing chamber shown in FIG. 3A,illustrating how a translating gas nozzle may be used instead of a gasinlet to introduce a gas-phase reactant into the process chamber.

FIG. 4 is a flowchart diagram illustrating one embodiment of a methodutilizing the techniques described herein.

FIG. 5 is a flowchart diagram illustrating another embodiment of amethod utilizing the techniques described herein.

FIG. 6 is a flowchart diagram illustrating yet another embodiment of amethod utilizing the techniques described herein.

DETAILED DESCRIPTION

Chemical reactions on surfaces can proceed using either vapor-phasereactants or liquid-phase reactants in contact with the surface. Wet ALEtypically relies on reactions between a surface and liquid-phasereactants, but vapor-phase reactants can also be used to deliverreactants to the surface. Sequential reactions can also be accomplishedby utilizing reactants from different phases, such as a gas-phasereactant followed by a liquid-phase reactant (or vice versa). Thepresent disclosure utilizes these concepts to provide a hybrid ALEprocess, which maintains the advantages of wet ALE, while avoiding thedisadvantages thereof.

In the hybrid ALE process described herein, a gas-phase reactant is usedto modify an exposed surface of a material to create a modified surfacelayer, and a liquid-phase reactant is used to selectively dissolve themodified surface layer without dissolving the material underlying themodified surface layer. Once the modified surface layer is selectivelydissolved, the substrate may be dried and the gas-phase surfacemodification and liquid-phase dissolution steps may be repeated for oneor more ALE cycles until a desired amount of the material is etched.

In some embodiments, the exposed surface of the material may be exposedto the gas-phase reactant and the liquid-phase reactant in sequence. Inother embodiments, the exposed surface of the material may be exposed toa liquid-phase reactant, while a gas-phase reactant is supplied to theprocess chamber. When a liquid-phase reactant is dispensed in thepresence of a gas-phase reactant, the liquid-phase reactant dispensedonto the exposed surface of the material displaces the gas-phasereactant from the exposed surface to prevent further surfacemodification of the exposed surface. When dispensed in such a manner,the liquid-phase reactant not only dissolves the modified surface layer,but also partitions the gas-phase surface modification and liquid-phasedissolution steps. This decreases the cycle time and improves thethroughput of the hybrid ALE process described herein, compared to otherALE techniques, by avoiding the need to perform a purge step between thesurface modification and dissolution steps.

Cycle time and throughput may be further improved in the hybrid ALEprocess described herein by performing the gas-phase surfacemodification and liquid-phase dissolution steps within the same processchamber. In one example implementation, the gas-phase surfacemodification and liquid-phase dissolution steps may both be performedwithin a spin chamber. In some embodiments, the gas-phase surfacemodification and liquid-phase dissolution steps may be performed withinthe same process chamber at roughly the same temperature and pressure.In one example implementation, the gas-phase surface modification andliquid-phase dissolution steps may be performed at (or near) atmosphericpressure and room temperature. Performing the gas-phase surfacemodification and liquid-phase dissolution steps within the same processchamber at roughly the same temperature and pressure decreases the cycletime and improves the throughput of the hybrid ALE process describedherein by avoiding unnecessary chamber transitions andtemperature/pressure changes.

The techniques described herein offer multiple advantages over otheretch techniques. For example, the techniques described herein providethe benefits of ALE, such as precise control of total etch amount,control of surface roughness, and improvements in wafer-scaleuniformity. The techniques described herein also provide variousbenefits of wet etching, such as the simplicity of the etch chamber,self-limiting reactions at near atmospheric temperature and pressureetching conditions, and reduced surface roughness. Unlike conventionalwet ALE processes, which tend to be slow, the techniques describedherein provide a hybrid ALE process that improves cycle time andthroughput by combining a gas-phase surface modification step with aliquid-phase dissolution step.

The techniques described herein may be performed on a wide variety ofsubstrates having a wide variety of layers and features formed thereon.In general, the substrates utilized with the techniques disclosed hereinmay be any substrates for which the etching of material is desirable.For example, the substrate may be a semiconductor substrate having oneor more semiconductor processing layers (all of which together maycomprise the substrate) formed thereon. In one embodiment, the substratemay be a substrate that has been subject to multiple semiconductorprocessing steps which yield a wide variety of structures and layers,all of which are known in the substrate processing art. In oneembodiment, the substrate may be a semiconductor wafer including thevarious structures and layers formed.

The techniques described herein may be used to etch a wide variety ofmaterials. Such materials may include polycrystalline materials,single-crystalline materials and amorphous materials. In someembodiments, the techniques described herein may be used to etch a metalmaterial such as, but not limited to, transition metals and noblemetals. In one exemplary embodiment, the material to be etched may be apolycrystalline transition metal such as, for example, molybdenum (Mo).Although the techniques described herein are discussed below withrelation to etching molybdenum, it will be recognized by those skilledin the art that such an example is merely exemplary and the techniquesdescribed herein may be used to etch a wide variety of other materials.For example, the techniques described herein may be used to etch othertransition metals such as, but not limited to, tungsten (W), vanadium(V), niobium (Nb), tantalum (Ta), and chromium (Cr).

FIG. 1 illustrates one example of a hybrid ALE process in accordancewith the present disclosure. More specifically, FIG. 1 illustratesexemplary steps performed during one cycle of a hybrid ALE process. Inthe process shown in FIG. 1, a polycrystalline material 105 surroundedby a dielectric material 110 is exposed to a gas-phase reactant 115during a surface modification step 100 to modify exposed surfaces of thepolycrystalline material 105 and create a modified surface layer 120. Insome embodiments, the polycrystalline material 105 to be etched can be,e.g., a transition metal. In one example embodiment, the polycrystallinematerial 105 may include molybdenum (Mo). In some embodiments, thegas-phase reactant 115 may be included within oxygen-containing gaseousenvironment. For example, the gas-phase reactant 115 may be a gas-phaseoxidizing agent including, for example, oxygen (O₂), ozone (O₃),nitrogen dioxide (NO₂) and/or a halogen gas. When exposed surfaces ofthe polycrystalline material 105 are exposed to the oxygen-containinggaseous environment, or the gas-phase oxidizing agent included therein,the exposed surfaces are oxidized to form a self-limiting oxidized layer(e.g., a molybdenum oxide, such as MoO₃) overlying the unmodifiedpolycrystalline material.

Oxidation is often used as a surface modification step in ALE. Manyoxidizers such as oxygen (O₂) and ozone (O₃) are easy to deliver atatmospheric pressure and room temperature. These oxidizers will formself-limiting oxide layers on many materials, such as metals, at roomtemperature. Although not strictly limited to such, these metals caninclude transition metals, and more specifically, polycrystallinetransition metals such as, for example, molybdenum (Mo) metal.

In the surface modification step 100 shown in FIG. 1, a chemicalreaction (e.g., oxidation) occurs at the exposed surface of thepolycrystalline material 105 to form the modified surface layer 120(e.g., a self-limiting oxidized layer, such as a molybdenum oxide). Insome cases, the reaction may be fast and self-limiting—i.e., thereaction product may modify one or more monolayers of the exposedsurface of the polycrystalline material 105, but may prevent any furtherreaction between the gas-phase reactant 115 and the underlyingpolycrystalline material 105.

In some embodiments, the modified surface layer 120 may be exposed toone or more liquid-phase reactants to selectively dissolve the modifiedsurface layer 120. For example, the modified surface layer 120 may beexposed to a complexing agent 125 dissolved in a liquid solvent 135(e.g., an aqueous or non-aqueous solution) during a complexation step130. In the complexation step 130, the complexing agent 125 (e.g., acarboxylate-based ligand) binds to the modified surface layer 120 (e.g.,a self-limiting oxidized layer) to form a ligand-metal complex 140. Insome embodiments, the complexing agent 125 may include a ligand (e.g.,α-benzoin oxime), which selectively binds to higher oxidation states ofthe polycrystalline material 105 (e.g., Mo⁶⁺) and causes the modifiedsurface layer 120 (e.g., MoO₃) to react with the ligand dissolved in theliquid solvent 135 to form a ligand-metal complex 140 that is soluble ina subsequent dissolution step 150. However, non-selective ligands canalso be used to bind to the modified surface layer 120 and form aligand-metal complex 140, as described in more detail below.

After oxidation and complexation, the polycrystalline material 105 isbrought in contact with a liquid solvent 145 in dissolution step 150 toselectively dissolve the modified surface layer 120 (e.g., MoO₃) withoutdissolving the underlying polycrystalline material 105 (e.g., metallicMo). This can be accomplished through one of two distinct methodologies:reactive dissolution or ligand binding followed by dissolution.

In reactive dissolution, the ligand is dissolved in a liquid solvent 135that can dissolve both the ligand and the ligand-metal complex 140 inthe dissolution step 150. This enables ligand binding and dissolution tobe accomplished using a single solvent 135/145. Thus, in reactivedissolution, the ligand binding and dissolution steps have at leastpartial temporal overlap.

In the reactive dissolution method, the modified surface layer 120(e.g., MoO₃) reacts with the ligand in the liquid solvent 135/145 toform a soluble ligand-metal complex 140, which dissolves in the liquidsolvent 135/145 to remove the modified surface layer 120. Any thicknessof the modified surface layer 120 (e.g., MoO₃) can be removed using thismethod. Selectivity comes from the ability of the ligand to bind tohigher oxidation states of the polycrystalline material 105 (e.g.,Mo⁶⁺), but not to lower oxidation states or unmodified portions of thepolycrystalline material 105. Reactive dissolution is not self-limiting,so the oxidation step must be self-limiting for the overall process toremain so.

In the ligand binding followed by dissolution method, the ligand bindingand dissolution steps have no temporal overlap. In this method, theligand is dissolved in a liquid solvent 135 in which the ligand-metalcomplex 140 is insoluble. The ligand within the liquid solvent 135reacts with the modified surface layer 120 (e.g., MoO₃) to form aninsoluble layer of ligand-metal complex 140. This layer is dissolved inthe dissolution step 150 when the surface is rinsed with a differentliquid solvent 145 in which the ligand-metal complex 140 is soluble. Inthe ligand binding followed by dissolution method, removal of themodified surface layer 120 (e.g., MoO₃) is limited by ligand packingdensity on the surface. The ligand binding in complexation step 130, andtherefore, the dissolution of the ligand-metal complex 140 in thedissolution step 150, is self-limiting.

Once the modified surface layer 120 is dissolved, the ALE etch cycle maybe completed by drying the surface of the substrate in a drying step160. In one embodiment, the surface of the substrate may be dried instep 160 by supplying a gas stream of air or nitrogen to the substrate.In another embodiment, the surface of the substrate may be dried in step160 by performing a spin dry step. In some embodiments, a drying aid(such as, e.g., isopropyl alcohol, IPA) may be dispensed onto thesurface of the substrate (not shown in FIG. 1) to further assist indrying the substrate before performing a spin dry step. Once the surfaceof the substrate is dry, the surface modification step 100, complexationstep 130, dissolution step 150 and drying step 160 shown in FIG. 1 maybe repeated for one or more ALE cycles until a desired amount of thepolycrystalline material 105 has been removed.

As noted above, the hybrid ALE cycle shown in FIG. 1 may be used for Moetching, in some embodiments. In this etch scheme, oxidation may beaccomplished by exposing the Mo surface to a gas-phase oxidizing agent,such as ozone. Ozone, being both more oxidizing and more reactive thanmolecular oxygen, forms a different self-limiting oxide compared to thelayer formed on air exposure. In particular, ozone exposure forms aself-limiting molybdenum trioxide (MoO₃) layer on the exposed Mosurface. After oxidation, the self-limiting molybdenum trioxide (MoO₃)layer can be selectively removed by ligand-assisted dissolution in anappropriate solvent.

One good ligand choice for the Mo etch process is α-benzoin oxime. Theα-benzoin oxime ligand selectively binds to Mo⁶⁺ ions, so MoO₃ willreact with the ligand to form a molybdenum α-benzoin oximate (i.e., aligand-metal complex), while metallic molybdenum will not react. Thischemical selectivity allows ligand binding and dissolution to beaccomplished in single solvent (such as, e.g. dimethyl sulfoxide(DMSO)). By exposing the MoO₃ surface layer to a solution of α-benzoinoxime dissolved in DMSO, the MoO₃ surface layer is converted to amolybdenum α-benzoin oximate, which is then dissolved in the DMSO. Inthis example, the ligand binding and dissolution step is self-limitingbecause metallic molybdenum does not react with α-benzoin oxime. Forother non-selective ligands, self-limiting behavior can be maintained byseparating the ligand binding and dissolution into sequential stepsusing a different solution (i.e., a different liquid solvent 135 and145) for each process step.

The self-limiting and selective behavior of the individual reactionsteps described above is shown in FIG. 2A. More specifically, FIG. 2Aillustrates a graph 200 depicting exemplary etch amounts (expressed innanometers, nm) that may be achieved over time (expressed in minutes,min) when attempting to etch a molybdenum (Mo) surface using: (a)UV-ozone oxidation alone, and (b) a solution of α-benzoin oxime andDMSO. As shown in FIG. 2A, the Mo surface will not etch even after 20minutes of exposure to ozone in a UV-ozone cleaner. This shows that thereaction between Mo and ozone is self-limiting at room temperature.Similarly, a Mo surface will not etch in an α-benzoin oxime solution inDMSO. No etching is observed even after 20 minutes of exposure. Thisshows that α-benzoin oxime will not react with metallic or low oxidationstate Mo.

FIG. 2B illustrates a graph 250 depicting exemplary etch amounts (nm)that may be achieved as a function of cycle number for when a UV-ozoneoxidation step, an α-benzoin oxime ligand binding (complexation) stepand a DMSO dissolution step are used to etch a Mo surface using thehybrid ALE process disclosed herein. In the example shown in FIG. 2B,one ALE cycle consists of placing the Mo coupon in a UV-ozone cleanerfor 1 minute followed by a 10 second dip in a 50 mM α-benzoin oximesolution in DMSO. Excess DMSO and unbound α-benzoin oxime (complexingagent) was removed with an acetone rinse and the coupon was then driedusing compressed air. In another example, another drying gas may beused, for example nitrogen (N₂). The thickness of the Mo layer wascalculated from 4-point probe resistivity measurements conducted every 5cycles. As shown in FIG. 2B, the etching is substantially linear withcycle number after the first nanometer of etching. Etching was observedfor samples exposed to both UV and ozone, as well as ozone alone, duringthe oxidation step. This indicates that ozone is necessary for the Mohybrid ALE process, but UV illumination is not. FIGS. 2A and 2B furthershow that no Mo material is removed by exposure to either reactant alone(FIG. 2A), but Mo material is removed (FIG. 2B) with the cyclic hybridALE process shown in FIG. 1 and described herein.

The hybrid ALE process shown in FIG. 1 causes smoothing of the etchedsurface. To observe the etched surface, scanning electron microscope(SEM) images of an as-deposited Mo film and a Mo film etched using thehybrid ALE scheme described above were obtained. No pitting orpreferential grain boundary etching was observed in the etched sample.Additionally, the thickness of the etched sample calculated from 4-pointprobe resistivity measurements was observed to match the thicknessmeasured in the SEM cross section. While the roughness of the Mo filmdid not increase during etching using the hybrid ALE process describedabove, particulate contamination (likely from the acetone rinse step)was observed.

The hybrid ALE process described herein may be used for etching a widevariety of materials including polycrystalline materials,single-crystalline materials and amorphous materials. In someembodiments, the hybrid ALE process described herein may be used foretching a polycrystalline material, such as a transition metal (e.g.,molybdenum, Mo), and a gas-phase oxidizing agent (e.g., oxygen, O₂, orozone, O₃) may be used to oxidize an exposed surface of the transitionmetal to form a self-limiting oxidized layer (such as, e.g., Mo03), asdescribed above. The oxidation of transition metals, such as molybdenum,is self-limiting when performed at (or near) room temperature. After theexposed surface of the transition metal is exposed to the gas-phaseoxidizing agent and the self-limiting oxidized layer is formed, one ormore liquid-phase reactants may be dispensed onto the surface of thesubstrate to selectively dissolve the self-limiting oxidized layer, sothat the self-limiting oxidized layer is removed without etching theunderlying polycrystalline material. Several different chemistries canbe used to selectively dissolve molybdenum oxides (e.g., MoO₃) withoutdissolving metallic Mo are described in more detail below.

In some embodiments, for example, a MoO₃ surface layer may be exposed toa ligand (such as α-benzoin oxime) dissolved in a non-aqueous solution(such as DMSO). When exposed to α-benzoin oxime dissolved in DMSO, theMoO₃ surface layer is converted to a molybdenum α-benzoin oximate, whichis then dissolved in the DMSO. In addition to DMSO, however, α-benzoinoxime is soluble in water, alcohol, acetone, methyl-ethyl ketone (MEK),and other ketones. The α-benzoin oxime ligand selectively binds to Mo⁶⁺ions, including the MoO₃ surface layer, to form a Mo-α-benzoin oximecomplex, which is soluble in acetone, DMSO, and other ketones, but notin alcohol or water. This chemical selectivity allows ligand binding anddissolution to be accomplished in a single solvent containing acetone,DMSO, and other ketones, for example. Alternatively, the ligand bindingand dissolution can be performed in sequential, non-overlapping steps,using for example water or alcohol in a first step, and acetone, DMSO,and other ketones, in a second sequential step.

In addition to α-benzoin oxime, other ligands can be used to selectivelybind to Mo⁶⁺ to form an alternative ligand-metal complex without bindingto metallic molybdenum (Mo) or low oxidation state Mo. Examples of suchligands include, but are not limited to, toluene dithiol, cupferron and8-hydroxyquinoline. Like α-benzoin oxime, these ligands selectively bindto Mo⁶⁺ to form a ligand-metal complex, which is soluble in non-aqueoussolutions. For example, the Mo-toluene dithiol complex is soluble inacetates (e.g. ethyl, butyl, and amyl acetate), and carbontetrachloride. Toluene dithiol, but not the Mo complex is soluble inaqueous solutions and alcohols. The Mo-cupferron complex is soluble inchloroform, concentrated nitric acid, or concentrated ammoniumhydroxide. Cupferron but not the Mo complex is soluble in neutralaqueous solutions. The Mo-8-hydroxyquinoline complex is soluble inconcentrated mineral acids. 8-hydroxyquinoline, but not the Mo complexis soluble in ethanol, acetone, chloroform, and benzene. Any of theligands mentioned above may be used in the ligand binding followed bydissolution method described above to selectively dissolve the MoO₃surface layer.

Reactive dissolution of the MoO₃ surface layer can also be accomplishedin aqueous solutions. For example, concentrated hydrochloric acid (HCl)may be used to dissolve molybdenum oxides selectively to metallic Mo.The measured Mo etch rate for 0.1 M, 1 M, 5 M, and 12 M HCl is belownormal detection thresholds (e.g., <0.01 nm/min). These sameconcentrations of HCl will dissolve a monolayer of MoO3 in <2 sec,giving a selectivity of more than 800:1. In addition to HCl, othermineral acids (such as sulfuric acid) may be used to dissolve molybdenumoxides. In some cases, sulfuric acid (H₂SO₄) may be preferred over HClfrom a materials compatibility perspective. The availability of HCl andsulfuric acid (and other mineral acids) at high purity and low cost,their use in many other semiconductor processes, and their performancein the selective removal of MoO₃ ensure that mineral acids are one ofthe preferred aqueous chemistries used for the selective dissolution ofMoO₃ in the hybrid ALE process described herein. Concentrated ammoniumhydroxide (NH₄OH) can also be used to dissolve molybdenum oxides,however, the selectivity versus metallic Mo is not as good as forconcentrated NH₄OH as it is for HCl.

Using aqueous chemistries for the selective dissolution of MoO₃ providesseveral advantages. They use inexpensive commodity chemicals, arereasonably environmentally friendly, and lack the flammability risk oforganic solvents. However, aqueous solutions of ammonium hydroxide(NH4OH) and concentrated mineral acids (such as HC1) will react withmany different metals. This may cause selectivity concerns if multiplemetals are present on the wafer surface during Mo etch. This leads tothe advantage of the non-aqueous chemistries, namely that ligand-metalcomplexation can be very selective between metals. For example,α-benzoin oxime is very selective to Mo⁶⁺ over most other metals. It isused in quantitative analysis to separate Mo from solutions containingmany other metal ions. However, the advantage of selectivity from usingthese ligands comes at the expense of additional chemical cost andflammability risk of using organic solvents.

Although described above for Mo etching, one skilled in the art wouldreadily understand how the hybrid ALE process shown in FIG. 1 may beused for etching other transition metals. For example, α-benzoin oximebinds to other ions as well as molybdenum. This includes ligand-metalcomplexes with tungsten, palladium, vanadium, niobium, tantalum, andchromium. There will be inherent selectivity with other metals that donot bind with α-benzoin oxime. Selectivity to other metals that complexwith α-benzoin oxime can still be achieved. While α-benzoin oxime willbind to the transition metals listed above, the solubility of theligand-metal complexes created with such metals are different fordifferent solutions. While molybdenum oximate is soluble in DMSO, forexample, tungsten oximate is not, so selectivity is achieved during thedissolution step. However, both molybdenum and tungsten oximatecomplexes are soluble in chloroform.

Room temperature processing is a big advantage of wet and hybrid ALEover thermal ALE. This advantage stems from the mechanism by which themodified layer is removed. In thermal ALE, the modified layer is removedthrough volatilization when material is taken from the solid phase intothe gas phase. This phase change requires the addition of latent heatand is limited by the vapor pressure of the modified layer. Thermalenergy is used to replace the intermolecular interactions that stabilizethe modified layer on the surface, so high temperatures are oftenrequired to remove the modified layer.

Unlike thermal ALE, the modified layer is dissolved into solution in wetand hybrid ALE. This process creates a solvation shell around themolecules as they dissolve. Interactions between solvent and solutereplace the intermolecular interactions in the solid. This solvationenergy, rather than thermal energy, drives the dissolution. Thefundamental difference in energy required for dissolution compared tovaporization explains why wet and hybrid ALE is viable at roomtemperature while thermal ALE is not. As solvation energy stronglydepends on the solvent species, an appropriate solvent must be chosen todissolve the modified layer in the hybrid ALE process described herein.For surfaces made of multiple materials, the different solvationenergies for the different components provides another pathway to deriveselectivity.

While the hybrid ALE process described herein can be accomplished usingmany different process chambers, tools and apparatuses, the processingequipment used to perform the hybrid ALE process is preferably capableof running at (or near) room temperature and at (or near) atmosphericpressure. In one example implementation, the hybrid ALE processdescribed herein may be performed within a spin chamber. When a spinchamber is utilized, liquid-phase reactants are dispensed from a nozzlepositioned over the substrate and are distributed by the rotationalmotion of a spin chuck on which the substrate is disposed. Gas-phasereactants (e.g., a gas-phase oxidizing agent, such as oxygen or ozone)can also be dispensed from a nozzle, which can be translated over theentire substrate surface to ensure the whole surface receives anequivalent dose of the gas-phase reactant (see, e.g., FIG. 3C).Alternatively, gas-phase reactants may be dispensed from a gas inlet,which introduces the gas-phase reactants into the spin chamber to createan oxygen-containing gaseous environment (see, e.g., FIG. 3A). The useof gas-phase reactants requires the spinner (otherwise referred to as aspin chuck) to be contained in a gas-tight enclosure with an exhaustoutlet and appropriate exhaust remediation such as an ozone destructmodule. In some embodiments, the spinner may be housed in a gas-tightenclosure that contains a static pressure of the gas-phase reactant.

FIG. 3A illustrates one embodiment of a processing system 300 that mayuse the hybrid ALE techniques described herein to etch a material on asurface of a substrate 330. As shown in FIG. 3A, the processing system300 includes a process chamber 310, which in some embodiments, may be apressure controlled chamber. In the embodiment shown in FIG. 3A, theprocess chamber 310 is a spin chamber having a spinner 320 (or spinchuck), which is configured to spin or rotate at a rotational speed. Asubstrate 330 is held on the spinner 320, for example, via electrostaticforce or vacuum pressure. In one example, the substrate 330 may be asemiconductor wafer having a material (such as, e.g., a polycrystallinematerial) formed on or within the substrate 330.

The processing system 300 shown in FIG. 3A further includes a liquidnozzle 340, which is positioned over the substrate 330 for dispensingliquid-phase reactants 342 onto a surface of the substrate 330, and agas inlet 350 positioned above the substrate 330 for introducinggas-phase reactants 352 into the process chamber 310. In someembodiments, the polycrystalline material formed on or within thesubstrate 330 may be a transition metal (such as, e.g., molybdenum, Mo)and a gas-phase reactant 352, such as a gas-phase oxidizing agent (suchas, e.g., O₂ or O₃), may be introduced into the process chamber 310 viathe gas inlet 350 to create an oxygen-containing gaseous environment.The oxygen-containing gaseous environment oxidizes exposed surfaces ofthe transition metal to form a self-limiting oxidized layer (such as,e.g., MoO₃). After the oxidized layer is formed, one or moreliquid-phase reactants 342 may be dispensed onto the surface of thesubstrate 330 via the liquid nozzle 340 to selectively dissolve theoxidized layer, so that the oxidized layer is removed without etchingthe underlying polycrystalline material. Examples of liquid-phasereactants 342 that may be used to selectively bind with and dissolve theoxidized layer are discussed in more detail above.

The liquid-phase reactant(s) 342 may be stored within a chemical supplysystem 346, which may include one or more reservoirs for holding thevarious liquid-phase reactant(s) 342 and a chemical injection manifold,which is fluidly coupled to the process chamber 310 via a liquid supplyline 344. In operation, the chemical supply system 346 may selectivelyapply desired chemicals to the process chamber 310 via the liquid supplyline 344 and the liquid nozzle 340 positioned within the process chamber310. Thus, the chemical supply system 346 can be used to dispense theliquid-phase reactant(s) 342 onto the surface of the substrate 330.

The gas-phase reactants 352 may be stored within a gas supply system356, which may include one or more reservoirs for holding the variousgas-phase reactants 352 and a gas injection manifold, which is coupledto the process chamber 310 via a gas supply line 354. In operation, thegas supply system 356 may selectively apply a desired gas-phase reactantto the process chamber 310 via the gas supply line 354 and the gas inlet350 positioned within the process chamber 310. Thus, the gas supplysystem 356 can be used to introduce gas-phase reactants 352 into theprocess chamber 310.

Because gas-phase reactants 352 are used, process chamber 310 maycomprise a gas-tight enclosure, which is capable of maintaining a staticpressure of the gas-phase reactant. The process chamber 310 may furtherinclude a gas exhaust outlet 370 for removing the gas-phase reactants352 and a drain 380 for removing the liquid-phase reactants 342 from theprocess chamber 310. In some embodiments, the gas exhaust outlet 370 maybe coupled to an appropriate exhaust remediation (not shown), such as anozone destruct module.

Components of the processing system 300 can be coupled to, andcontrolled by, a controller 360, which in turn, can be coupled to acorresponding memory storage unit and user interface (not shown).Various processing operations can be executed via the user interface,and various processing recipes and operations can be stored in a storageunit. Accordingly, a given substrate 330 can be processed within theprocess chamber 310 in accordance with a particular recipe. In someembodiments, a given substrate 330 can be processed within the processchamber 310 in accordance with an etch recipe that utilizes the hybridALE techniques described herein.

The controller 360 shown in block diagram form in FIG. 3A can beimplemented in a wide variety of manners. In one example, the controller360 may be a computer. In another example, the controller 360 mayinclude one or more programmable integrated circuits that are programmedto provide the functionality described herein. For example, one or moreprocessors (e.g., microprocessor, microcontroller, central processingunit, etc.), programmable logic devices (e.g., complex programmablelogic device (CPLD), field programmable gate array (FPGA), etc.), and/orother programmable integrated circuits can be programmed with softwareor other programming instructions to implement the functionality of aproscribed plasma process recipe. It is further noted that the softwareor other programming instructions can be stored in one or morenon-transitory computer-readable mediums (e.g., memory storage devices,flash memory, dynamic random access memory (DRAM), reprogrammablestorage devices, hard drives, floppy disks, DVDs, CD-ROMs, etc.), andthe software or other programming instructions when executed by theprogrammable integrated circuits cause the programmable integratedcircuits to perform the processes, functions, and/or capabilitiesdescribed herein. Other variations could also be implemented.

As shown in FIG. 3A, the controller 360 may be coupled to variouscomponents of the processing system 300 to receive inputs from, andprovide outputs to, the components. For example, the controller 360 maybe coupled to: the process chamber 310 for controlling the temperatureand/or pressure within the process chamber 310; the spinner 320 forcontrolling the rotational speed of the spinner 320; the chemical supplysystem 346 for controlling the various liquid-phase reactants 342dispensed onto the substrate 330; and the gas supply system 356 forcontrolling the various gas-phase reactants 352 introduced into theprocess chamber 310. The controller 360 may control other processingsystem components not shown in FIG. 3A, as is known in the art.

In some embodiments, the controller 360 may control the variouscomponents of the processing system 300 in accordance with an etchrecipe that utilizes the hybrid ALE techniques described herein. Forexample, the controller 360 may supply various control signals to thegas supply system 356, which cause the gas supply system 356 tointroduce a gas-phase reactant 352 into the process chamber 310 tocreate a modified surface layer on the substrate 330. Likewise, thecontroller 360 may supply various control signals to the chemical supplysystem 346, which cause the chemical supply system 346 to dispense oneor more liquid-phase reactants 342 onto the surface of the substrate 330to selectively dissolve the modified surface layer without dissolvingthe material underlying the modified surface layer. Example gas-phasereactants 352 and liquid-phase reactants 342 for modifying an exposedsurface of a polycrystalline molybdenum (Mo) material and selectivelydissolving the modified Mo surface layer are discussed above.

In some embodiments, the controller 360 may control the timing of thegas-phase surface modification step and the liquid-phase dissolutionstep performed during each cycle of the hybrid ALE process. In oneembodiment, the controller 360 may control timing of the gas-phasesurface modification and the liquid-phase dissolution steps, so that thesurface of the substrate 330 is exposed to the gas-phase reactant 352and the one or more liquid-phase reactants 342 in sequence with notemporal overlap. In another embodiment, the controller 360 may controltiming of the gas-phase surface modification and the liquid-phasedissolution steps, so that the one or more liquid-phase reactants 342are dispensed onto the surface of the substrate while the substrate isexposed to the gas-phase reactant 352.

Once the modified surface layer is selectively dissolved, the substrate330 may be dried and the gas-phase surface modification and liquid-phasedissolution steps may be repeated for one or more ALE cycles until adesired amount of the polycrystalline material is etched. In someembodiments, the controller 360 may supply control signals to thespinner 320 and/or the chemical supply system 346 to dry the substrate330. In one example, the controller 360 may control the rotational speedof the spinner 320, so as to dry the substrate 330 in a spin dry step.In another example, control signals supplied from the controller 360 tothe chemical supply system 346 may cause a drying agent (such as, e.g.,isopropyl alcohol) to be dispensed onto the surface of the substrate 330to further assist in drying the substrate before performing the spin drystep.

The gas-phase surface modification, liquid-phase dissolution and spindry steps of the hybrid ALE process described herein are each performedwithin the same process chamber 310. In some embodiments, the controller360 may control the temperature and/or the pressure within the processchamber 310, so that the gas-phase surface modification, liquid-phasedissolution and spin dry steps are performed at roughly the sametemperature and pressure. In other words, the temperature and/orpressure within the process chamber 310 may be relatively constantduring the gas-phase surface modification, liquid-phase dissolution andspin dry steps of the hybrid ALE process described herein. As usedherein, a “relatively constant” temperature and/or pressure is one thatchanges no more than 20% between processing steps. In one exampleimplementation, the gas-phase surface modification, liquid-phasedissolution and spin dry steps may each be performed at (or near)atmospheric pressure and room temperature. Performing the processingsteps within the same process chamber at roughly the same temperatureand pressure decreases the cycle time and improves the throughput of thehybrid ALE process described herein by avoiding unnecessary chambertransitions and temperature/pressure changes.

It is noted, however, that the embodiments described herein are notstrictly limited to only atmospheric pressure and room temperature, norare they limited to a particular process chamber. In other embodiments,one or more processing steps of the hybrid ALE process described hereincan be run at above atmospheric pressure in a pressure vessel, or atreduced pressure in a vacuum chamber. Liquid-phase reactants can bedispensed in these environments as long as the vapor pressure of theliquid is lower than the chamber pressure. For these implementations, aspinner with a liquid dispensing nozzle would be placed in the pressurevessel or vacuum chamber. The temperature of the liquid being dispensedcan be elevated to any temperature below its boiling point at thepressure of the process. Higher liquid temperatures can increase thekinetics of dissolution.

In some embodiments of the hybrid ALE process described herein, thesubstrate 330 may be exposed to gas-phase reactant(s) 352 andliquid-phase reactant(s) 342 in sequence. In other embodiments, however,the substrate 330 may be exposed to one or more liquid-phase reactants342 while a gas-phase reactant 352 is supplied to the process chamber310. When a liquid-phase reactant 342 is dispensed in the presence of agas-phase reactant 352, the liquid-phase reactant 342 dispensed onto thesurface of the substrate 330 displaces the gas-phase reactant 352 fromthe surface to prevent further modification of the surface. Whendispensed in such a manner, the liquid-phase reactant 342 not onlydissolves the modified surface layer, but also partitions the gas-phasesurface modification and liquid-phase dissolution steps. Thispartitioning or segregation of processing steps is shown schematicallyin FIG. 3B and further improves the cycle time and throughput of thehybrid ALE process described herein, compared to other ALE techniques,by avoiding the need to perform a purge step between the surfacemodification and dissolution steps.

A magnified view of a portion 390 of the substrate 330 is shown in FIG.3B to illustrate the partitioning of the gas-phase surface modificationand liquid-phase dissolution steps. In the hybrid ALE process describedherein, gas-phase reactant(s) 352 are introduced into the processchamber 310 to create, for example, an oxygen-containing gaseousenvironment. The gas-phase reactant(s) 352 react with exposed surfacesof the substrate 330 to form a self-limiting modified surface layer 335.Next, one or more liquid-phase reactants 342 are dispensed onto thesurface of the substrate 330 in the presence of the gas-phase reactant352 while the spinner 320 is rotating. In some embodiments, thecontroller 360 may control the rotational speed of the spinner 320during the liquid-phase dissolution step, so that the one or moreliquid-phase reactants 342 are dispensed onto the surface of thesubstrate 330 in the presence of the gas-phase reactant 352 while thespinner is rotating at a first rotational speed. As spinner 320 rotatesat the first rotational speed, the liquid-phase reactant(s) 342propagate outward along the surface of the substrate 330 (in thedirection shown in FIG. 3B) to dissolve the modified surface layer 335.The liquid-phase reactant(s) 342 prevent the gas-phase reactant 352 fromreaching the surface of the substrate 330, and thus, provide dissolutionof the modified surface layer 335 while preventing underlying portionsof the substrate 330 from being re-oxidized.

As the liquid-phase reactant(s) 342 propagate outward (in the directionshown in FIG. 3B), the gas-phase reactant(s) 352 are displaced from thesurface of the substrate 330. This displacement happens because theliquid-phase reactant(s) 342 create a continuous film on the surfacethat makes it difficult or substantially prevents the gas-phasereactant(s) 352 from reaching the surface of the substrate 330. Forexample, the gas-phase reactants 352 must diffuse through theliquid-phase reactant(s) 342 to reach the surface of the substrate 330.Once the modified surface layer 335 is dissolved by the liquid-phasereactant(s) 342, however, the liquid-phase reactant(s) 342 can beflushed from the surface of the substrate 330 to re-expose the surfaceto the gas-phase reactant(s) 352 and create a new modified surfacelayer. Exposure to the gas-phase reactant(s) 352 can be accomplished, insome embodiments, by spin-drying the substrate 330. Because theliquid-phase reactant(s) 342 can be flushed from the surface of thesubstrate 330 at a rate faster than the diffusion timescale of thegas-phase reactant(s) 352 into the liquid, the cyclic dispensing of theliquid-phase reactant(s) 342 during the liquid-phase dissolution stepeffectively partitions the gas-phase surface modification andliquid-phase dissolution steps.

There are numerous ways in which the liquid-phase reactant(s) 342 can beflushed from the surface of the substrate 330. In some embodiments, thegas inlet 350 (or gas nozzle 355) may be configured to supply a gasstream of air or nitrogen to the substrate 330 to dry the surface of thesubstrate 330. In other embodiments, the controller 360 may control therotational speed of the spinner 320, so as to dry the substrate 330 in aspin dry step. In one example implementation, the controller 360 maycontrol the rotational speed of the spinner 320 during the spin dryingstep, so that the spinner 320 rotates at a second rotational speed,which is greater than the first rotational speed. In some embodiments,the liquid nozzle 340 may be configured to dispense a drying aid (suchas, e.g., isopropyl alcohol) onto the surface of the substrate 330 tofurther assist in drying the substrate before the spin dry step isperformed.

In the embodiment shown in FIGS. 3A and 3B, reactions arephase-separated based on reactant partition coefficients. In one exampleimplementation, the gas:liquid concentration ratio used for thegas-phase surface modification and liquid-phase dissolution steps may beapproximately 100:1 when using oxygen in the gas-phase surfacemodification and water in the liquid-phase dissolution step. As notedabove, the liquid-phase reactant(s) 342 dispensed during theliquid-phase dissolution step block the gas-phase reactant 352 fromreaching the surface of the substrate 330, due to low gas solubility. Insome embodiments, the partition coefficient can be improved by adding anoxygen scavenger.

It is recognized that the processing system 300 shown in FIGS. 3A-3Brepresents only one example of a processing system that can be utilizedto etch a substrate using the hybrid ALE process described herein.However, the techniques described herein are not strictly limited to theexample processing system 300 shown in FIGS. 3A-3B and may beaccomplished using many different process chambers, tools andapparatuses.

In the processing system 300 shown in FIG. 3A, for example, the hybridALE process described herein is performed within a process chamber 310having a spinner 320 on which the substrate 330 is disposed. In otherwords, the hybrid ALE process steps are performed within a spin chamber.When a spin chamber is utilized, the liquid-phase reactant(s) 342dispensed from the liquid nozzle 340 are distributed by the rotationalmotion of the spinner 320. When the liquid-phase reactant(s) 342 aredispensed in the presence of a gas-phase reactant 352, the rotationalmotion of the spinner 320 causes the liquid-phase reactant(s) 342 topropagate outward along the surface of the substrate 330 to dissolve themodified surface layer 335 and prevent the gas-phase reactant 352 fromreaching the surface of the substrate 330 and re-oxidizing underlyingportions of the substrate 330. However, the hybrid ALE process describedherein is not strictly limited to a spin chamber embodiment, and may beperformed in other process chambers, tools and apparatuses that do nothave a spinner.

In the processing system 300 shown in FIG. 3A, a liquid nozzle 340 ispositioned over the substrate 330 for dispensing the liquid-phasereactant(s) 342 onto the surface of the substrate 330, and a gas inlet350 is positioned above the substrate 330 for introducing a gas-phasereactant 352 (e.g., a gas-phase oxidizing agent) into the processchamber 310 to create an oxygen-containing gaseous environment withinthe process chamber 310. It is recognized, however, that theliquid-phase reactant(s) 342 and/or the gas-phase reactant 352 may besupplied to the process chamber 310 by a variety of other means. Forexample, the gas-phase reactant 352 can be dispensed from a translatinggas nozzle 355, as shown in FIG. 3C.

FIG. 3C provides a top down view into the process chamber 310 shown inFIG. 3A. As shown in FIG. 3C, process chamber 310 may alternativelyinclude a gas nozzle 355, instead of the gas inlet 350, to introduce agas-phase reactant 352 (e.g., a gas-phase oxidizing agent) into theprocess chamber 310. In the embodiment shown in FIG. 3C, the gas nozzle355 can be translated over the surface of the substrate to dispense thegas-phase reactant 352 onto the surface of the substrate 330.Translating the gas nozzle 355 over the entire substrate surface ensuresthat the whole surface receives an equivalent dose of the gas-phasereactant 352. In some embodiments, the translating gas nozzle 355 may beused to dry the substrate 330 and oxidize the exposed surface of thematerial in a single step. In such embodiments, the oxidizerconcentration at the gas/substrate interface may be higher than thegas/liquid interface.

The techniques described herein offer multiple advantages over otheretch techniques. For example, the techniques described herein providethe benefits of ALE, such as precise control of total etch amount,control of surface roughness, and improvements in wafer-scaleuniformity. The techniques described herein also provide variousbenefits of wet etching, such as the simplicity of the etch chamber,self-limiting reactions at (or near) atmospheric pressure and roomtemperature etching conditions, and reduced surface roughness.

Unlike conventional wet ALE processes, which tend to be slow, thetechniques described herein provide a hybrid ALE process that improvescycle time and throughput by combining the gas-phase surfacemodification and liquid-phase dissolution steps. As noted above, cycletime and throughput are improved in the hybrid ALE process describedherein by performing the gas-phase surface modification and liquid-phasedissolution steps in the same process chamber at roughly the sametemperature and pressure. As such, the hybrid ALE process describedherein provides a cyclic etch process that combines gas-phase andliquid-phase precursors without requiring separate process chambers orlong thermalization times. In some embodiments, cycle time andthroughput are further improved by dispensing the liquid-phasereactant(s) onto a surface of the substrate in the presence of thegas-phase reactant(s), so that the liquid-phase reactant(s) displace thegas-phase reactant(s) from the surface and partition or segregate thegas-phase surface modification and liquid-phase dissolution steps. Usingthe liquid-phase reactant(s) to partition the gas-phase surfacemodification and liquid-phase dissolution steps enables fast transitionsbetween processing steps, and in some cases, may improve cycle time andthroughput by lowering or even eliminating purge times betweenprocessing steps.

The hybrid ALE process described herein also expands the number ofreactants available for surface modification and ligand binding. Avariety of gas-phase reactants are disclosed above for modifying anexposed surface of molybdenum (Mo). A variety of liquid-phase reactantsare also provided above for ligand binding and dissolution of thesubsequently formed Mo-ligand complexes. While reactants disclosed aboveprovide a new ALE etch chemistry for Mo, the hybrid ALE processdescribed above can be adjusted for etching a wide variety of othermaterials using different etch chemistries. Selectivity can be achievedusing differences in ligand binding or differences in solubility of themetal-ligand complexes.

FIGS. 4-6 illustrate exemplary methods that use the hybrid ALEtechniques described herein. More specifically, FIGS. 4-6 illustratevarious embodiments of methods used to provide a hybrid ALE process,which maintains the advantages of wet ALE, while avoiding thedisadvantages thereof, by combining a gas-phase surface modificationstep with a liquid-phase dissolution step for etching a substratedisposed within a process chamber. It will be recognized that theembodiments of FIGS. 4-6 are merely exemplary and additional methods mayutilize the hybrid ALE techniques described herein. Further, additionalprocessing steps may be added to the methods shown in the FIGS. 4-6 asthe steps described are not intended to be exclusive. Moreover, theorder of the steps is not limited to the order shown in the figures asdifferent orders may occur and/or various steps may be performed incombination or at the same time.

FIG. 4 illustrates one embodiment of a method 400 that may be used foretching a substrate using a hybrid atomic layer etching (ALE) process.The method 400 shown in FIG. 4 comprises receiving the substrate, thesubstrate having a material exposed (in step 410). Then, in step 420,the method 400 includes selectively etching the material by performingmultiple cycles of the hybrid ALE process, wherein each cycle comprises:(a) performing a gas-phase surface modification step to chemicallymodify an exposed surface of the material and provide a modified surfacelayer, wherein the gas-phase surface modification step includes exposingthe substrate to a gas-phase reactant to chemically modify the exposedsurface of the material; and (b) performing a liquid-phase dissolutionstep to selectively dissolve the modified surface layer of the material,wherein the liquid-phase dissolution step includes dispensing one ormore liquid-phase reactants onto a surface of the substrate to dissolvethe modified surface layer. In the method 400 shown in FIG. 4, the oneor more liquid-phase reactants are dispensed onto the surface of thesubstrate while the substrate is exposed to the gas-phase reactant. Insuch a method, the one or more liquid-phase reactants partition thegas-phase surface modification step and the liquid-phase dissolutionstep by displacing the gas-phase reactant from the surface of thesubstrate.

FIG. 5 illustrates another embodiment of a method 500 that may be usedfor etching a substrate using a hybrid atomic layer etching (ALE)process. The method 500 shown in FIG. 5 comprises receiving thesubstrate, the substrate having a polycrystalline material exposed (instep 510). Then, in step 520, the method 500 includes selectivelyetching the polycrystalline material by performing multiple cycles ofthe hybrid ALE process, wherein each cycle comprises: (a) chemicallymodifying an exposed surface of the polycrystalline material to providea modified surface layer, wherein said exposed surface is chemicallymodified by oxidation of the polycrystalline material using a gas-phaseoxidizing agent; (b) binding a complexing agent to the modified surfacelayer of the polycrystalline material to provide a complex-boundmodified surface layer; and (c) selectively removing the complex-boundmodified surface layer of the polycrystalline material by exposing thecomplex-bound modified surface layer to a liquid solvent, whichdissolves the complex-bound modified surface layer without dissolvingthe polycrystalline material underlying the complex-bound modifiedsurface layer.

FIG. 6 illustrates yet another embodiment of a method 600 that may beused for etching a substrate using a hybrid atomic layer etching (ALE)process. The method 600 shown in FIG. 6 comprises receiving thesubstrate, the substrate having a molybdenum (Mo) metal exposed (in step610). Then, in step 620, the method 600 includes selectively etching theMo metal by performing multiple cycles of the hybrid ALE process,wherein each cycle comprises: (a) chemically modifying an exposedsurface of the Mo metal to provide a modified surface layer, whereinsaid exposed surface is chemically modified by oxidation of the Mo metalusing a gas-phase oxidizing agent containing ozone; (b) binding acomplexing agent to the modified surface layer of the Mo metal toprovide a complex-bound modified surface layer; and (c) selectivelyremoving the complex-bound modified surface layer of the Mo metal byexposing the complex-bound modified surface layer to a liquid solvent,which dissolves the complex-bound modified surface layer withoutdissolving the Mo metal underlying the complex-bound modified surfacelayer, and wherein b) and c) have at least partial temporal overlap.

It is noted that reference throughout this specification to “oneembodiment” or “an embodiment” means that a particular feature,structure, material, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention, butdo not denote that they are present in every embodiment. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarilyreferring to the same embodiment of the invention. Furthermore, theparticular features, structures, materials, or characteristics may becombined in any suitable manner in one or more embodiments. Variousadditional layers and/or structures may be included and/or describedfeatures may be omitted in other embodiments.

The term “substrate” as used herein means and includes a base materialor construction upon which materials are formed. It will be appreciatedthat the substrate may include a single material, a plurality of layersof different materials, a layer or layers having regions of differentmaterials or different structures in them, etc. These materials mayinclude semiconductors, insulators, conductors, or combinations thereof.For example, the substrate may be a semiconductor substrate, a basesemiconductor layer on a supporting structure, a metal electrode or asemiconductor substrate having one or more layers, structures or regionsformed thereon. The substrate may be a conventional silicon substrate orother bulk substrate comprising a layer of semi-conductive material. Asused herein, the term “bulk substrate” means and includes not onlysilicon wafers, but also silicon-on-insulator (“SOI”) substrates, suchas silicon-on-sapphire (“SOS”) substrates and silicon-on-glass (“SOG”)substrates, epitaxial layers of silicon on a base semiconductorfoundation, and other semiconductor or optoelectronic materials, such assilicon-germanium, germanium, gallium arsenide, gallium nitride, andindium phosphide. The substrate may be doped or undoped.

Systems and methods for processing a substrate are described in variousembodiments. The substrate may include any material portion or structureof a device, particularly a semiconductor or other electronics device,and may, for example, be a base substrate structure, such as asemiconductor substrate or a layer on or overlying a base substratestructure such as a thin film. Thus, substrate is not intended to belimited to any particular base structure, underlying layer or overlyinglayer, patterned or unpatterned, but rather, is contemplated to includeany such layer or base structure, and any combination of layers and/orbase structures.

One skilled in the relevant art will recognize that the variousembodiments may be practiced without one or more of the specificdetails, or with other replacement and/or additional methods, materials,or components. In other instances, well-known structures, materials, oroperations are not shown or described in detail to avoid obscuringaspects of various embodiments of the invention. Similarly, for purposesof explanation, specific numbers, materials, and configurations are setforth in order to provide a thorough understanding of the invention.Nevertheless, the invention may be practiced without specific details.Furthermore, it is understood that the various embodiments shown in thefigures are illustrative representations and are not necessarily drawnto scale.

Further modifications and alternative embodiments of the describedsystems and methods will be apparent to those skilled in the art in viewof this description. It will be recognized, therefore, that thedescribed systems and methods are not limited by these examplearrangements. It is to be understood that the forms of the systems andmethods herein shown and described are to be taken as exampleembodiments. Various changes may be made in the implementations. Thus,although the hybrid ALE techniques are described herein with referenceto specific embodiments, various modifications and changes can be madewithout departing from the scope of the present disclosure. Accordingly,the specification and figures are to be regarded in an illustrativerather than a restrictive sense, and such modifications are intended tobe included within the scope of the present disclosure. Further, anybenefits, advantages, or solutions to problems that are described hereinwith regard to specific embodiments are not intended to be construed asa critical, required, or essential feature or element of any or all theclaims.

What is claimed is:
 1. A system configured to etch a substrate using ahybrid atomic layer etching (ALE) process, the system comprising: aprocess chamber configured to receive the substrate; a gas supply systemcoupled to the process chamber and configured to store a gas-phasereactant; a chemical supply system coupled to the process chamber andconfigured to store one or more liquid-phase reactants; and a controllerprogrammed to control process conditions within the process chamberwhile multiple cycles of the hybrid ALE process are performed to etch amaterial exposed on the substrate, wherein each cycle includes agas-phase surface modification step and a liquid-phase dissolution step,and wherein the controller is configured to supply: a first set ofcontrol signals to the gas supply system during the gas-phase surfacemodification step, wherein the first set of control signals cause thegas supply system to introduce the gas-phase reactant into the processchamber to expose the substrate to the gas-phase reactant, chemicallymodify an exposed surface of the material and provide a modified surfacelayer of the material; and a second set of control signals to thechemical supply system during the liquid-phase dissolution step, whereinthe second set of control signals cause the chemical supply system todispense the one or more liquid-phase reactants onto a surface of thesubstrate to selectively dissolve the modified surface layer withoutdissolving the material underlying the modified surface layer.
 2. Thesystem of claim 1, wherein the material includes a transition metal. 3.The system of claim 2, wherein the material comprises molybdenum (Mo),tungsten (W), vanadium (V), niobium (Nb), tantalum (Ta), or chromium(Cr).
 4. The system of claim 2, wherein the gas-phase reactant is agas-phase oxidizing agent, which oxidizes the exposed surface of thematerial to form a self-limiting oxide layer.
 5. The system of claim 4,wherein the process chamber further comprises a gas inlet, which iscoupled to receive the gas-phase oxidizing agent from the gas supplysystem, and wherein the gas inlet is configured to introduce thegas-phase oxidizing agent into the process chamber to create anoxygen-containing gaseous environment within the process chamber.
 6. Thesystem of claim 4, wherein the process chamber further comprises a gasnozzle, which is coupled to receive the gas-phase oxidizing agent fromthe gas supply system, and wherein the gas nozzle is configured totranslate over the surface of the substrate to dispense the gas-phaseoxidizing agent onto the surface of the substrate.
 7. The system ofclaim 4, wherein the one or more liquid-phase reactants comprise anaqueous solution, which selectively dissolves and removes theself-limiting oxide layer without dissolving the material underlying theself-limiting oxide layer.
 8. The system of claim 4, wherein the one ormore liquid-phase reactants comprise a complexing agent dissolved in afirst liquid solvent, and wherein the complexing agent binds to theself-limiting oxide layer to form a ligand-metal complex.
 9. The systemof claim 8, wherein the ligand-metal complex is soluble in the firstliquid solvent, and wherein the first liquid solvent dissolves theligand-metal complex and removes the self-limiting oxide layer.
 10. Thesystem of claim 8, wherein the one or more liquid-phase reactantsfurther comprise a second liquid solvent, which is different from thefirst liquid solvent, wherein the ligand-metal complex is insoluble inthe first liquid solvent and soluble in the second liquid solvent, andwherein the second liquid solvent dissolves the ligand-metal complex andremoves the self-limiting oxide layer.
 11. The system of claim 1,wherein the process chamber further comprises a gas inlet or a gasnozzle, which is configured to supply a gas stream of air or nitrogen tothe substrate to dry the surface of the substrate.
 12. The system ofclaim 1, wherein the process chamber further comprises a spinnerconfigured to rotate at a rotational speed, wherein the substrate isheld on the spinner, and wherein the controller is configured to controlthe rotational speed of the spinner to dry the surface of the substrate.13. A system configured to etch a substrate using a hybrid atomic layeretching (ALE) process, the system comprising: a process chamberconfigured to receive the substrate; a gas supply system coupled to theprocess chamber and configured to store a gas-phase reactant; a chemicalsupply system coupled to the process chamber and configured to store oneor more liquid-phase reactants; and a controller programmed to controlprocess conditions within the process chamber while multiple cycles ofthe hybrid ALE process are performed to etch a material exposed on thesubstrate, wherein each cycle includes a gas-phase surface modificationstep and a liquid-phase dissolution step, and wherein the controller isconfigured to supply: a first set of control signals to the gas supplysystem during the gas-phase surface modification step, wherein the firstset of control signals cause the gas supply system to introduce thegas-phase reactant into the process chamber to expose the substrate tothe gas-phase reactant, chemically modify an exposed surface of thematerial and provide a modified surface layer of the material; a secondset of control signals to the chemical supply system during theliquid-phase dissolution step, wherein the second set of control signalscause the chemical supply system to dispense the one or moreliquid-phase reactants onto a surface of the substrate to selectivelydissolve the modified surface layer without dissolving the materialunderlying the modified surface layer; wherein the controller isprogrammed to control timing of the gas-phase surface modification stepand the liquid-phase dissolution step performed during each cycle of thehybrid ALE process, so that the one or more liquid-phase reactants aredispensed onto the surface of the substrate while the substrate isexposed to the gas-phase reactant; and wherein the one or moreliquid-phase reactants dispensed during the liquid-phase dissolutionstep segregate the gas-phase surface modification step from theliquid-phase dissolution step by displacing the gas-phase reactant fromthe surface of the substrate.
 14. The system of claim 13, wherein theprocess chamber further comprises a spinner configured to rotate at arotational speed, wherein the substrate is held on the spinner, andwherein the controller controls the rotational speed of the spinnerduring the liquid-phase dissolution step, so that the one or moreliquid-phase reactants are dispensed onto the surface of the substratein the presence of the gas-phase reactant while the spinner is rotatingat a first rotational speed.
 15. The system of claim 14, whereinrotation of the spinner at the first rotational speed causes the one ormore liquid-phase reactants to propagate outward along the surface ofthe substrate to dissolve the modified surface layer and prevent thegas-phase reactant from reaching the surface of the substrate andre-oxidizing underlying portions of the substrate.
 16. The system ofclaim 15, wherein after the liquid-phase dissolution step is performedto selectively dissolve the modified surface layer, the controllercontrols the rotational speed of the spinner during a spin drying stepto flush the one or more liquid-phase reactants from the surface of thesubstrate and re-expose the exposed surface of the material to thegas-phase reactant in a subsequent gas-phase surface modification step.17. The system of claim 16, wherein the controller controls therotational speed of the spinner during the spin drying step, so that thespinner rotates at a second rotational speed, which is greater than thefirst rotational speed.
 18. A system configured to etch a substrateusing a hybrid atomic layer etching (ALE) process, the systemcomprising: a process chamber configured to receive the substrate; a gassupply system coupled to the process chamber and configured to store agas-phase reactant; a chemical supply system coupled to the processchamber and configured to store one or more liquid-phase reactants; anda controller programmed to control process conditions within the processchamber while multiple cycles of the hybrid ALE process are performed toetch a material exposed on the substrate, wherein each cycle includes agas-phase surface modification step and a liquid-phase dissolution step,and wherein the controller is configured to supply: a first set ofcontrol signals to the gas supply system during the gas-phase surfacemodification step, wherein the first set of control signals cause thegas supply system to introduce the gas-phase reactant into the processchamber to expose the substrate to the gas-phase reactant, chemicallymodify an exposed surface of the material and provide a modified surfacelayer of the material; and a second set of control signals to thechemical supply system during the liquid-phase dissolution step, whereinthe second set of control signals cause the chemical supply system todispense the one or more liquid-phase reactants onto a surface of thesubstrate to selectively dissolve the modified surface layer withoutdissolving the material underlying the modified surface layer; andwherein the controller is programmed to control a temperature and apressure within the process chamber, so that the gas-phase surfacemodification step and the liquid-phase dissolution step are performed atroughly the same temperature and the same pressure.
 19. The system ofclaim 18, wherein the controller is programmed to control thetemperature and the pressure within the process chamber, so that thegas-phase surface modification step and the liquid-phase dissolutionstep are both performed at or near atmospheric pressure and roomtemperature.
 20. The system of claim 18, wherein the controller isprogrammed to control the temperature and/or the pressure within theprocess chamber, so that the temperature and/or the pressure changes nomore than 20% between the gas-phase surface modification step and theliquid-phase dissolution step.